Behavioral work in both rats and pigs will be conducted with a major objective in identifying the components of the learning process that are influenced by malnutrition and environmental stimulation. There will also be an extension of work on cholinergic enzymes of brain in relationship to malnutrition and stimulation. The variable in these studies would be to provide stimulation at different vulnerable periods both concurrently with malnutrition and also following rehabilitation from malnutrition. Various forms and degrees of stimulation will be provided. Both protein metabolism and energy metabolism will be studied in the malnourished and the early malnourished and control rat. In energy metabolism studies there will be particular attention given to the contribution of activity to the increased total energy metabolism that has been noted in the previously malnourished rat. Bibliographic references: Tigner, Joseph C. and Richard H. Barnes. Effect of postnatal malnutrition on plasma corticosteroid levels in male albino rats. Proc. Soc. Experimental Biology and Medicine 149: 80-82, 1975. Levitsky, David A., Thomas F. Massaro and Richard H. Barnes. Maternal malnutrition: and the neonatal environment. Fed. Proc. 34: No. 7, 1583-1586,1975.